In printing apparatuses known to the applicant, especially in printing apparatuses that employ ink of the melt type (i.e. ink which is liquid at an elevated temperature and is generated by melting solid ink elements, such as so-called toner pearls or ink pearls), solid ink pearls are melted by a melting device and fed through a filter via a collection chamber into a reservoir, from which a drop forming unit of a print-head is supplied with ink. The filter is employed to remove particles such as non-melted ink or contaminants from the liquid ink before the ink reaches the reservoir to avoid jetting instability or blockages in the drop forming unit, especially in the drop forming nozzles.
In conventional printing apparatus employing a melt-type of ink, the melting device is located fixed relative to the filter. Accordingly, the ink fed to the filter from the melting device tends to flow via the same path from the collection chamber to the reservoir, which usually is a direct path from the location where the ink enters. This has the disadvantage, however, that ink which accumulates in other areas of the collection chamber tends to remain for longer periods of time and these areas are only poorly supplied with fresh ink. This may create so-called “dead zones” within the chamber in which very little renewal of the ink takes place and the ink becomes prone to degradation. In particular, such dead zones may prevent proper operation of the ink supply system as the older ink may produce a different print quality and may also generate particles through crystallisation. The development of such dead zones can significantly shorten the lifetime of the printing apparatus.